Most of the 29 million Americans with type 2 diabetes (T2D) do not achieve recommended levels of physical activity (PA), and such inactivity is linked with major T2D complications and death. Unfortunately, many existing interventions to improve activity in T2D are intensive and difficult to implement in clinical care settings. Motivational interviewing (MI), a more widely applied technique, is associated with some improvement in PA among T2D patients. However, MI alone may not improve PA sufficiently to reduce rates of major adverse outcomes. Positive psychology (PP) interventions, which utilize simple activities to increase optimism and boost confidence, have led to improvements in PA and related behaviors in prior trials in medical populations. PP may therefore be an additional, novel method to promote PA in T2D patients. Combining the well-being focus of PP with the targeted behavioral approach of MI may have a greater impact on PA than either intervention alone. Our team has successfully developed a combined PP-MI intervention for cardiac patients that is simple to deliver by phone and has been well-accepted in this medical population. However, a PP-MI intervention has never been developed or tested in inactive T2D patients, despite the great ongoing need for PA interventions in this population that are both feasible and effective. To address this gap, we are customizing our PP-MI intervention to meet the needs of T2D patients, using data from: (i) our team's pilot study of a PP intervention in T2D and (ii) qualitative interviews with inactive T2D patients that explore barriers to PA and gather feedback on the proposed PP-MI intervention. We now propose a randomized pilot trial of the customized 16-week phone-based PP-MI intervention in 60 T2D patients who have low PA. The PP-MI intervention will consist of a written treatment manual and phone sessions with study clinicians to review assigned PP activities and set MI-based activity goals. This program will also have participants complete a neighborhood walkability audit to increase their awareness of local opportunities for PA, and it will additionally focus on the reduction of sedentary time. PP-MI will be compared to an attention-matched standard MI condition that uses a treatment manual, goal-setting, and a parallel call schedule. Consistent with the R21 grant mechanism, the study's primary outcomes will be feasibility and acceptability, as measured by rates of PP-MI phone session completion and participant ratings of the ease and utility of phone sessions. As a main secondary outcome, we will compare between-group improvements in moderate or greater intensity PA, measured by accelerometer, at 16 and 32 weeks. Finally, we will explore between-group differences in psychological, behavioral, and medical outcomes, including hemoglobin A1c. If this intervention is feasible, well-accepted, and associated with improvements in PA, we will test it in a larger R01 efficacy trial powered to detect effects on PA, glycemic control, and major clinical outcomes.